1. Field of the Invention
The present invention relates to a planographic printing plate supply unit and more particularly, a planographic printing plate supply unit which supplies pairs of planographic printing plates and covering papers one by one from a stacking bundle in which the planographic printing plates and the covering papers are stacked alternately.
2. Description of the Related Art
Generally, an image recording face of a planographic printing plate is covered with a protective covering paper attached thereto and a plurality of these units are stacked in a thickness direction so as to compose a bundle of the planographic printing plates. If an image is recorded on the planographic printing plate with an exposure unit or the like, it is necessary to pick up the planographic printing plates one by one from the bundle and supply then to the exposure unit.
For example, according to an image recording material sheeting unit described in Japanese Patent Application Laid-Open (JP-A) No. 2003-182904, printing plates and covering papers are stacked alternately in a cassette of the sheet transporting portion and a sucker suctions the covering paper and planographic printing plate from above the covering paper and raises them to bring them out of the cassette. After the printing plate and covering paper are taken out, the covering paper is separated from the suctioned printing plate by means of a fan. However, because the structure uses the sucker to supply the printing plate, there are concerns that the structure may become complicated and cost may increase.
Contrary to this, JP-A No. 60-202028 has disclosed a structure in which the covering paper is fed out by a roller and the planographic printing plate is sent out by a vacuum pad. However, according to this configuration, because the planographic printing plates or the covering papers are taken out one by one, a next planographic printing plate cannot be taken out until the covering paper is taken out, thereby taking much time. Further, because the planographic printing plate and the covering paper each need a taking-out mechanism, the quantity of components increases thereby possibly inducing increases in size of the unit and manufacturing costs.
Although conveying a planographic printing plate and a covering paper with a roller as a pair is conceivable, often only a planographic printing plate is carried separately from the covering paper or two pairs of the planographic printing plate and the covering paper are carried simultaneously due to penetration of air into gaps between the planographic printing plates.